X-Git-Url: http://git.rot13.org/?a=blobdiff_plain;f=kernel%2Fkthread.c;h=4f9c60ef95e83d9dd08aaeff106d602ad7d41051;hb=47585d8f5dea10dea49c948f1fb13ef7632409c7;hp=e75950a1092c6b2063ea24a1f196f987e7f21bf5;hpb=18ce920a6eba05c0d55cdc95fbbadf7e4c4b457b;p=powerpc.git

diff --git a/kernel/kthread.c b/kernel/kthread.c
index e75950a109..4f9c60ef95 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -12,6 +12,7 @@
 #include <linux/unistd.h>
 #include <linux/file.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <asm/semaphore.h>
 
 /*
@@ -41,9 +42,16 @@ struct kthread_stop_info
 
 /* Thread stopping is done by setthing this var: lock serializes
  * multiple kthread_stop calls. */
-static DECLARE_MUTEX(kthread_stop_lock);
+static DEFINE_MUTEX(kthread_stop_lock);
 static struct kthread_stop_info kthread_stop_info;
 
+/**
+ * kthread_should_stop - should this kthread return now?
+ *
+ * When someone calls kthread_stop on your kthread, it will be woken
+ * and this will return true.  You should then return, and your return
+ * value will be passed through to kthread_stop().
+ */
 int kthread_should_stop(void)
 {
 	return (kthread_stop_info.k == current);
@@ -114,11 +122,32 @@ static void keventd_create_kthread(void *_create)
 		create->result = ERR_PTR(pid);
 	} else {
 		wait_for_completion(&create->started);
+		read_lock(&tasklist_lock);
 		create->result = find_task_by_pid(pid);
+		read_unlock(&tasklist_lock);
 	}
 	complete(&create->done);
 }
 
+/**
+ * kthread_create - create a kthread.
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @namefmt: printf-style name for the thread.
+ *
+ * Description: This helper function creates and names a kernel
+ * thread.  The thread will be stopped: use wake_up_process() to start
+ * it.  See also kthread_run(), kthread_create_on_cpu().
+ *
+ * When woken, the thread will run @threadfn() with @data as its
+ * argument. @threadfn can either call do_exit() directly if it is a
+ * standalone thread for which noone will call kthread_stop(), or
+ * return when 'kthread_should_stop()' is true (which means
+ * kthread_stop() has been called).  The return value should be zero
+ * or a negative error number; it will be passed to kthread_stop().
+ *
+ * Returns a task_struct or ERR_PTR(-ENOMEM).
+ */
 struct task_struct *kthread_create(int (*threadfn)(void *data),
 				   void *data,
 				   const char namefmt[],
@@ -153,6 +182,15 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
 }
 EXPORT_SYMBOL(kthread_create);
 
+/**
+ * kthread_bind - bind a just-created kthread to a cpu.
+ * @k: thread created by kthread_create().
+ * @cpu: cpu (might not be online, must be possible) for @k to run on.
+ *
+ * Description: This function is equivalent to set_cpus_allowed(),
+ * except that @cpu doesn't need to be online, and the thread must be
+ * stopped (i.e., just returned from kthread_create().
+ */
 void kthread_bind(struct task_struct *k, unsigned int cpu)
 {
 	BUG_ON(k->state != TASK_INTERRUPTIBLE);
@@ -163,17 +201,24 @@ void kthread_bind(struct task_struct *k, unsigned int cpu)
 }
 EXPORT_SYMBOL(kthread_bind);
 
+/**
+ * kthread_stop - stop a thread created by kthread_create().
+ * @k: thread created by kthread_create().
+ *
+ * Sets kthread_should_stop() for @k to return true, wakes it, and
+ * waits for it to exit.  Your threadfn() must not call do_exit()
+ * itself if you use this function!  This can also be called after
+ * kthread_create() instead of calling wake_up_process(): the thread
+ * will exit without calling threadfn().
+ *
+ * Returns the result of threadfn(), or %-EINTR if wake_up_process()
+ * was never called.
+ */
 int kthread_stop(struct task_struct *k)
-{
-	return kthread_stop_sem(k, NULL);
-}
-EXPORT_SYMBOL(kthread_stop);
-
-int kthread_stop_sem(struct task_struct *k, struct semaphore *s)
 {
 	int ret;
 
-	down(&kthread_stop_lock);
+	mutex_lock(&kthread_stop_lock);
 
 	/* It could exit after stop_info.k set, but before wake_up_process. */
 	get_task_struct(k);
@@ -184,21 +229,18 @@ int kthread_stop_sem(struct task_struct *k, struct semaphore *s)
 
 	/* Now set kthread_should_stop() to true, and wake it up. */
 	kthread_stop_info.k = k;
-	if (s)
-		up(s);
-	else
-		wake_up_process(k);
+	wake_up_process(k);
 	put_task_struct(k);
 
 	/* Once it dies, reset stop ptr, gather result and we're done. */
 	wait_for_completion(&kthread_stop_info.done);
 	kthread_stop_info.k = NULL;
 	ret = kthread_stop_info.err;
-	up(&kthread_stop_lock);
+	mutex_unlock(&kthread_stop_lock);
 
 	return ret;
 }
-EXPORT_SYMBOL(kthread_stop_sem);
+EXPORT_SYMBOL(kthread_stop);
 
 static __init int helper_init(void)
 {
@@ -207,5 +249,5 @@ static __init int helper_init(void)
 
 	return 0;
 }
-core_initcall(helper_init);
 
+core_initcall(helper_init);